Centralizer



April 29, 1969 k. R. vl cENT ET AL I 3,441,323

' v I CENTRALIZER Fil ed' June 7, 1967 l v Sheet of 2 ROBERT R V/NCE/VT M5,? w/v C! HUFFMAN INVENTORS BY W ATTORNEY April 29, 1969 R; R. VINCENT ET AL CENTRALIZER Z of2 Sheet Filed June 7. 1967 United States Patent C US. Cl. 30s 3.9 4 Claims ABSTRACT OF THE DISCLOSURE A centralizer for drill rods, including pivoted jaws operated by pneumatic or hydraulic pressure, and consisting of a single actuating member for actuating the jaws between open and closed positions and for clamping a drill rod coupling between the jaws. The actuating member consists of a sliding cylinder with extensions having cam surfaces engaging corresponding surfaces on the jaws. The centralizer features a minimum number of moving parts, a slim profile in the plane perpendicular to the drill rod axis, and a coil spring lightly biasing the jaws in the closed position for minimizing danger to operating personnel.

Background of the invention A guiding device known as a drill rod centralizer is commonly used on rock drill equipment and similar earthworking devices. Centralizers are usually mounted on the drill mast or guide shell for guiding the drill rod during operation of the drill, and particularly when starting or collaring a hole.

Construction features common to popular forms of centralizers include two pivoted arms or jaws which close around the drill rod and are operable to be opened for inserting or removing lengths of drill steel when operations require.

Often, in mining and construction workings, the position of the distal end of the drill mast or guide shell is inaccessible to the operator due to the remoteness of the centralizer from the operators control station and possible considerable elevation of the distal end of the guide shell above ground level. It, therefore, becomes desirable to have remote control of the operation of the centralizer.

Remote controlled, fluid pressure actuated centralizers are known in the prior art, for example, those shown in US. Patent No. 2,365,680 issued to I. C. Curtis, and Patent No. 2,734,723 issued to J. A. Larcen. In Curtis, pressure fluid is applied to a piston which through considerable linkage actuates the guide jaws of the centralizer This linkage is not only subject to damage due to falling debris or possible collision with the walls of the workings during movement of the drill positioner assembly, but is inherently less reliable than the invention due to a multiplicity of moving parts. The centralizer of Larcen is an advancement in the reduction of moving parts, but as in Curtis has biasing means which hold the guide jaws in the open position when the pressure fluid is relieved in the piston chamber. This is inherently dangerous to personnel should the control means be accidently set to close the jaws while drill steel was being inserted or removed.

US. Patent No. 3,231,318 issued to S. L. Ytterfors also illustrates a centralizer operated by pressure fluid. Ytterfors centralizer occupies considerable area in the plane perpendicular to the drill rod axis which is undesirable when locating the drill positioner in proximity to adjacent wall surfaces in the drill workings. It is desirable to this end to minimize the bulk of the centralizer so that it presents a profile in the plane perpendicular to the axis of the drill guide shell no greater than the drill or guide shell.

3,441,323 Patented Apr. 29, 1969 Summary of the invention It will be appreciated that the invention disclosed herein represents an improvement in the art in that a drill steel centralizer operated by pressure fluid has substantially one moving part disposed to actuate the guide jaws of the centralizer, and by means of a simple yet effective camming action exerts a closing force of considerable magnitude on the guide jaws to retain them in the closed position even under heavy lateral forces exerted by the drill rod. The invention also renders an effective means for making up or breaking loose threaded drill steel joints by utilizing the guide jaws to forcibly clamp drill steel couplings in accomplishing this task.

A specific object of the invention is to provide reliable centralizer operating means simple in construction and self-protecting against damage from falling debris or careless handling.

Another aspect of the invention obviates a hazardous condition for operating personnel by providing biasing means to keep the guide jaws closed under light force when the centralizer is not connected to a source of pressure fluid.

The above noted features of the invention are accomplished by a centralizer characterized by compact construction, simplicity and reliability of operation, and low cost.

Brief description of the drawings FIG. 1 is an illustration of a typical universal type rock drill positioning and feeding assembly utilizing the centralizer design disclosed.

FIG. 1a is a schematic representation of a suitable control for the centralizer consisting of a four-way valve shown in one controlling position.

FIG. 1b illustrates the control valve of FIG. 1a in another controlling position.

FIG. 10 illustrates the control valve of FIGS. 1a and 1b in still another controlling position.

FIG. 2 is an enlarged fragmental view of the drill positioner shown in FIG. 1 illustrating the operation of the centralizer to hold a drill steel coupling while breaking out a joint.

FIG. 3 is a view along the axis of the drill rod showing the frontal configuration of the centralizer and the close lateral spacing between the centralizer and a vertical wall which is achievable in accordance with this invention.

FIGS. 4 and 5 are a complete section and a partial section, respectively, taken along the lines 4-4 and 55, respectively, of FIG. 6 illustrating the two working positions of the centralizer.

FIG. -6 is a side elevation of the preferred design of the invention.

Description of the preferred embodiments In FIG. 1, the invention, an improved pressure fluid operated centralizer, is shown in association with a pneumatic'rock drill and a positioning and feeding assembly therefor of a well-known type commonly used in the construction and mining industry. The centralizer, generally designated by numeral 10, is mounted on a centralizer bracket 12 which in turn is rigidly attached to the drill guide shell 14. The illustrative drill positioning and feeding assembly, designated in its entirety by numeral 15, is of the well-known universal type and may be positioned for a wide coverage pattern. The positioning assembly 15 includes fluid pressure operated cylinders 16 and 18 for positioning the boom 20 and additional cylinders 22 and 24 for swinging the guide shell 14 relative to the boom 20. The guide shell 14 carries the drill 28 which is mounted thereupon to be fed longitudinally along the guide shell 14 by a well-known type of feed 3 mechanism, not shown, which is actuated by a feed motor 30. A short section of drill steel known as a shank 32 is chucked in the drill 28 and is shown coupled to a longer section of drill rod 34 by means of an internally threaded coupling 36. In practice, drill rod sections are usually 4 feet to 12 feet in length and are coupled together during the drilling cycle to form drill strings of considerable length. The drill 28 contemplated is of a well-known percussive type and includes means for rotation of the chucked shank 32 in both directions during or independent of other operations. A drill bit 38 is threaded on the distal end of the drill rod 34; and, as illustrated in FIG. 1, the centralizer is particularly useful for guiding and supporting the drill rod 34 as the drill 28 is operated during starting or collating the hole 40 in the workface 42.

Also shown in FIG. 1 is a schematic representation of a typical control system for the centralizer 10 to be explained later in detail.

Details of the preferred embodiment of the invention are illustrated in FIGS. 4, 5 and 6. Referring first to FIG. 6, a U-shaped centralizer frame comprises a base plate 50 having spaced, upstanding members 51 and 52 welded thereto; and, the centralizer frame is welded to the centralizer bracket 12. The upstanding members 51 and 52 journal a pin 54 which forms the axis for a pair of pivoted jaws 56. A bushing 58 (FIG. 4) serves as a bearing element for the jaws 56 and is replaceable in the event of excessive wear. The centralizer jaws 56 are thus freely pivotable about the axis formed by the pin 54 between open and closed positions, and in the closed position (FIG. 5) the jaws 56 guide and support the forward end of the drill rod 34, particularly during starting or collaring of the hole in the manner shown in FIG. 1 and familiar to those knowledgeable in the art.

A pair of identical, reversely turned liners 60 are disposed in complementary cavities 62 in the jaws 56 and are removably attached by capscrews 64. In the closed position of the jaws 56 (FIG. 5), opposed surfaces 65 of the liners 60 coact to form a reduced bore 66 slightly larger in diameter than the drill rod 34. The bore 66 serves as the guiding surface and closely contains the drill rod 34 for rectilinear movement therethrough with respect to the workface 42 (FIG. 1).

Although the drill rod 34 shown is circular in cross section, it would be obvious to those skilled in the art that the liners 60 could be used with drill rods of noncircular cross section providing the greatest cross sectional dimension approaches but does not equal or exceed the diameter of the bore 66. It is also contemplated that the liners 60 are changeable to accommodate drill steels of various diameters or to be replaced if worn or damaged.

In the closed position of the jaws 56, as shown in FIGS. 5 and 6, opposed surfaces 68 coact to define openings 70 and 72 at opposite ends of the jaws 56. Openings 70 and 72 are coaxial with the bore 66 and are generally elliptical in shape. The dimension forming the minor diameter of the so-called elliptical shape is chosen such that the jaws 56 will not completely close around the drill steel coupling 36, but serve to clamp the coupling 36 against rotation when the drill 28 is operated to rotate a drill string to break loose or tighten the threaded joints of the drill string. The intersection of the reduced bore 66 with the openings 70 and 72 forms the stepped shoulders 74 and ,75 perpendicular to the axis of the bore 66.

Referring particularly to FIGS. 4 and 5, the centralizer includes a piston housing 76 which has a bore 78 and is coaxially slidable with respect to a stationary piston head 80. A cylindrical end cover 82 closing one end of the bore 78 is provided with a central opening which sealably surrounds a piston rod 84. The end cover 82 is retained in a slightly enlarged portion of the bore 78 by a conventional retaining ring 86. The end cover 82 sealably coacts with the piston housing 76 and the piston rod 84 to define a chamber 88, and further provides a guide for the piston housing 76.

The piston as previously described as consisting in part of a piston head and a piston rod 84 also includes a threaded rod extension extending through a hole 92 in the centralizer frame base plate 50 where a nut 94 serves as a means to fix the piston to the base plate 50. The piston head 80 sealably coacts with the bore 78 to form pressure fluid chambers 88 and 96. The piston rod 84 is provided with a cavity 98 for receiving a coiled compression spring 100 acting against the closed end 102 of cavity 98 and a shallow bore 104 in the piston housing 76. Provision for conducting pressure fluid to and from the chamber 88 is made by the drilled passage 106 in the piston rod communicating with passage 108 in the frame base plate 50. In like manner, passage 110 in the piston rod 84 in communication with a passage 112 in the frame base plate 50 serves the same function for chamber 96.

The opposite end of the piston housing 76 has integral bifurcated extension arms 114 disposed to engage the jaws 56 for opening and closing them in response to pressure fluid applied to chambers 88 or 96, respectively. Opening of the jaws 56 from the closed condition shown in FIG. 5 occurs in response to projections 116 on the bifurcated extension arms 114 engaging projecting lugs 118 on the jaws 56, and such opening is limited by the surfaces 120 on the extension arms 114 engaging in area contact with the cam surfaces 122 on the jaws 56, as shown in FIG. 4.

The closed position of the jaws 56 shown in FIG. 5 is attained in response to the upward movement of the piston housing 76 until the identical liners 60 abut to form the bore 66. In such closed position, the cam surfaces 124 on the extension arms 114 are in substantial area contact with the coacting cam surfaces 122 on the jaws 56.

In operation, pressure fluid, compressed air or hydraulic oil, for example, is supplied from a source, not shown, to the centralizer through a suitable control means such as a four-Way valve represented schematically in three operating positions in FIGS. 1a, 1b, and 1c. With the control valve 130 in the position of FIG. 1a, pressure fluid from an inlet conduit 132 will be supplied to chamber 96 through conduit 134 and passages 112 and 110. Simultaneously chamber 88 will discharge through passages 106 and 108, conduit 136 and through the control valve 130 to discharge conduit means 138. With pressure fluid applied to chamber 96 the housing 76 will extend with respect to the piston '84 resulting in a substantial clamping force applied to the jaws 56 from the extension arms 114 through the coacting cam surfaces 122 and 124 to hold the jaws 56 closed in drill steel guiding position (FIG. 5) or to forcibly grip a drill steel coupling 36 depending on the operation to be performed.

The position of the control valve 130 shown in FIG. 112 will cause the pressure fluid inlet conduit 132 to be blocked and both chambers 88 and 96 in the centralizer to be in communication via their respective conduit means with the discharge conduit 138. In this position of the valve 130, the jaws 56 will be resiliently urged to the closed position by the coil spring 100 acting on the piston housing 76 with light force.

In the position of valve 130 of FIG. 1c substantially the reverse condition of the aforedescribed control position FIG. la will exist; that is, chamber 88 will be supplied with pressure fluid and chamber 96 will be discharged. Under the influence of pressure fluid in chamber 88, the piston housing 76 "will retract to cause engagement of the projections 116 on the extension arms 114 with the lugs 118 on the jaws 56 and the resultant pivotal opening of the jaws 56 until surfaces 126 on the extension arms 114 engage the coacting cam surfaces 122 on the jaws 56 (FIG. 4).

Due to the fact that the jaws 56 will always close under the influence of the light force applied by the spring 100 prior to any substantial clamping force being applied, and will also be closed when the inlet of pressure fluid is blocked (FIG. 16, position) or disconnected, it can be appreciated that danger to operating personnel will be minimized in that the application of pressure fluid from the inlet with the control valve 130 in any position will not result in sudden violent closing of the jaws 56 as could be the case if the jaws 56 were biased to remain in the open position.

A typical drilling operation sequence commences with the jaws 56 open in response to the control valve position of FIG. 10. The drill rod 34 is positioned in the jaws 56 and screwed hand tight via the coupling 36 to the shank 32. Since normal drill rotation is in a direction tending to tighten the threads of the coupling-drill rod juncture, hand-tight engagement only is necessary, The jaws 56 are then closed by moving the control valve 130 through position 1b to la. The centralizer is now in drill steel guiding condition with the jaws forcibly clamped.

Prior to drilling the full feed length of the drill 28, the control valve 130 is moved to position FIG. to open the jaws 56 and allow the coupling 36 to move through the open centralizer jaws 56 to the position shown in FIG. 2. The jaws 56 are then closed around the coupling 36 and the surfaces 68 of the opening 70 forcibly grip the coupling 36 to prevent rotation thereof. The drill 28 is now rotated reversely to unscrew the shank 32 from the coupling 36 preparatory to retracting the drill 28 and the shank 32 in union along the guide shell 14. An additional section of drill rod and a second coupling may now be aligned to be added to the drill string by feeding and rotating the drill 28 to screw opposite ends of the rod into the clamped coupling 36 and the second coupling, the latter receiving the threaded end of the shank 32. After releasing the substantial clamping force on the coupling 36 by moving the control valve to the open position of FIG. 1c, the drill string may continue to be fed into the hole 40. Successive lengths of drill rod may be added in the same manner until the desired drilling depth is reached. By reversing the above described order of operation, it can be appreciated that the jaws 56 are used for gripping the drill steel couplings for successive unscrewing of the drill steel sections as they are withdrawn from the hole 40.

It is preferred when drilling in an upward direction, as shown in FIG. 2, that the opening 70 be used for clamping the coupling 36 wherein the stepped shoulder 74 will serve as an axial stop to prevent the drill string from slipping out of the hole 40 during drill rod section addition or deletion operations. As can be readily seen, the opening 72 and the stepped shoulder 75 are preferably used when drilling in a downward direction to prevent the drill string from slipping back into the hole.

FIG. 3 is illustrative of a particularly advantageous aspect of the invention in that a view along the axis of the drill rod 34 shows that the size and shape of the percussive drill 28 is the limiting factor in achieving proximity to a parallel wall 44 when drilling holes close to the sides of the workface. The reduced profile of the centralizer 10 owes to the compact, simplified actuating mechanism described hereinabove.

Particularly noteworthy in regard to the invention is the selection of the angle formed by the cam surfaces 124 on the extension arms 114 and the axis of the piston housing 76. An angle of 45 has proved to be most suitable in that a powerful wedging action is achieved to clamp the jaws 56 between the bifurcated extension arms 1 14, yet wear on the cam surfaces 124 and the coacting cam surfaces 122 of the jaws 56 can be taken up by only slight additional axial travel of the piston housing 76 in order for the centralizer to continue to perform its intended function. Also representing improvement in the art is the simple, rugged, and self-protecting character of the invention owing to the use of the combination of the frame members and the piston housing 7 6.

What is claimed is:

1. A drill steel centralizer comprising:

a frame;

drill steel engaging jaws mounted for movement on said frame;

a pressure fluid actuated power device including a piston fixed with respect to said frame and a movable member comprising an axially extensible and retractable housing for said piston;

engaging means on said movable member comprising extended portions of said piston housing having surfaces thereon engageable with coacting surfaces on said jaws; and,

biasing means comprising a coil spring member disposed in said housing urging said extended portions of said housing against said coacting surfaces on said jaws to hold said jaws in drill steel engaging position.

2. A drill steel centralizer mountable on the distal end of a rock drill guide shell, said centralizer comprising:

a frame including spaced upstanding members supported by a base member;

drill steel engaging jaws movably mounted on pivot means fixed in said spaced upstanding members;

a pressure fluid actuated power device comprising stationary piston and piston rod means mounted on said frame between said upstanding members and cylindrical piston housing means mounted over said piston and piston rod means, said piston housing being axially extensible and retractable with respect to said piston and piston rod means, and means on said piston housing for actuating said jaws.

3. The invention according to claim 2 wherein:

said piston housing includes bifurcated integral extensions thereof having sloped cam surface for engaging coacting cam surfaces on said jaws to hold said jaws in drill steel engaging position.

4. The invention set forth in claim 3 wherein:

said jaws include laterally projecting integral lugs located between said bifurcated extensions of said piston housing and said lugs are engageable by complementary projections on said bifurcated extensions whereby in response to the retraction of said piston housing said jaws are forcibly opened.

References Cited UNITED STATES PATENTS 1,822,501 9/1931 OnSrud 26932 X 2,365,680 12/ 1944 Curtis 3083.9 2,665,603 1/ 1954 Hoffman 26934 2,734,723 2/1956 Larcen 173-43 2,747,445 5/ 1956 McConnell 269-32 X 3,231,318 l1/ 1966 Ytterfors 3082.9

CARROLL B. DORITY, JR., Primary Examiner.

US. Cl. X.R. 269-32, 34 

